Proton-conducting membrane and its use

Abstract

A proton-conducting polymer membrane comprising at least one polyazole, at least one ionic liquid and at least one compound of the formula (P1) R I 4 POH  (P1) wherein R I , in each case mutually independently, is a residue which comprises C, O and/or H optionally together with further atoms differing therefrom, wherein two residues R I may optionally be joined to one another. The membrane is in particular distinguished by elevated mechanical stability and elevated conductivity and is therefore in particular suitable as a polymer electrolyte membrane for fuel cell applications.

1 - 19 . (canceled) 
     
     
         20 . A proton-conducting polymer membrane comprising at least one polyazole, at least one ionic liquid and at least one compound of the formula (P1)
   R I   4 POH  (P1)
   
       wherein R I , in each case mutually independently, is a residue which comprises C, O and/or H optionally together with further atoms differing therefrom, wherein two residues R I  may optionally be joined to one another. 
     
     
         21 . The proton-conducting polymer membrane according to  claim 20 , wherein the polyazole contains benzimidazole units of the formula 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       in which
 Ar are identical or different and denote a tetravalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 1  are identical or different and denote a divalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 2  are identical or different and denote a di- or trivalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 3  are identical or different and denote a trivalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 4  are identical or different and denote a trivalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 5  are identical or different and denote a tetravalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 6  are identical or different and denote a divalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 7  are identical or different and denote a divalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 8  are identical or different and denote a trivalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 9  are identical or different and denote a di- or tri- or tetravalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 10  are identical or different and a di- or trivalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 Ar 11  are identical or different and denote a divalent aromatic or heteroaromatic group, which may be mono- or polynuclear, 
 X is identical or different and denotes oxygen, sulfur or an amino group, which bears a hydrogen atom, a group comprising 1-20 carbon atoms, 
 R identically or differently denotes hydrogen, an alkyl group and an aromatic group and 
 n and m are identical or different and denote an integer greater than or equal to 10, 
 
       
         
           
           
               
               
           
         
       
       in which
 R identically or differently denotes an alkyl group and an aromatic group and 
 n 1  is an integer greater than or equal to 10. 
 
     
     
         22 . The proton-conducting polymer membrane according to  claim 21 , wherein X is identical or different and denotes oxygen, sulfur or an amino group, which bears a hydrogen atom, a group comprising 1-20 carbon atoms selected from a branched or unbranched alkyl or alkoxy group, or an aryl group as a further residue,
 n and m are identical or different and denote an integer greater than or equal to 100, and   n 1  is an integer greater than or equal to 100.   
     
     
         23 . The proton-conducting polymer membrane according to  claim 20 , wherein the membrane contains as ionic liquid (A), (B) or (C)
 (A) salts of the formula (IL-I)
   [A] n   + [Y] n−   (IL-I),
 
 in which 
 n denotes 1, 2, 3 or 4, 
 [A] +  denotes a quaternary ammonium cation, an oxonium cation, a sulfonium cation or a phosphonium cation and 
 [Y] n−  denotes a mono-, di-, tri- or tetravalent anion; 
   (B) mixed salts of the formulas (IL-IIa), (IL-IIb) or (IL-IIc)
 [A 1 ] + [A 2 ] +[Y]   n−  (IL-IIa), wherein n=2; 
 [A 1 ] + [A 2 ] + [A 3 ] + [Y] n−  (IL-IIb), wherein n=3; or 
 [A 1 ] + [A 2 ] + [A 3 ] + [A 4 ] + [Y] n−  (IL-IIc), wherein n=4 and 
 wherein [A 1 ] + , [A 2 ] + , [A 3 ] +  and [A 4 ] +  are mutually independently selected from the groups stated for [A] +  and [Y] n−  has the meaning stated in (A); or 
   (C) mixed salts of the formulas (IL-IIIa), (IL-IIIb), (IL-IIIc), (IL-IIId), (IL-IIIe), (IL-IIIf), (IL-IIIg), (IL-IIIh), (IL-IIIi) or (IL-IIIj)
 [A 1 ] + [A 2 ] + [A 3 ] + [M 1 ] + [Y] n−  (IL-IIIa), wherein n=4; 
 [A 1 ] + [A 2 ] + [M 1 ] + [M 2 ] + [Y] n−  (IL-IIIb), wherein n=4; 
 [A 1 ] + [M 1 ] + [M 2 ] + [M 3 ] + [Y] n−  (IL-IIIc), wherein n=4; 
 [A 1 ] + [A 2 ] + [M 1 ] + [Y] n−  (IL-IIId), wherein n=3; 
 [A 1 ] + [M 1 ] + [M 2 ] + [Y] n−  (IL-Ille), wherein n=3; 
 [A 1 ] + [M 1 ] + [Y] n−  (IL-IIIf), wherein n=2; 
 [A 1 ] + [A 2 ] + [M 4 ] 2+ [Y] n−  (IL-IIIg), wherein n=4; 
 [A 1 ] + [M 1 ] + [M 4 ] 2+ [Y] n−  (IL-IIIh), wherein n=4; 
 [A 1 ] + [M 5 ] 3+ [Y] n−  (IL-IIIi), wherein n=4; or 
 [A 1 ] + [M 4 ] 2+ [Y] n−  (IL-IIIj), wherein n=3 and 
 wherein [A 1 ] + , [A 2 ] +  and [A 3 ] +  are mutually independently selected from the groups stated for [A] + , [Y] n−  has the meaning stated in (A) and [M 1 ] + , [M 2 ] + , [M 3 ] +  mean monovalent metal cations, [M 4 ] 2+  means divalent metal cations and [M 5 ] 3+  means trivalent metal cations. 
   
     
     
         24 . The proton-conducting polymer membrane according to  claim 20 , wherein the ionic liquid has a melting point of less than 180° C. 
     
     
         25 . The proton-conducting polymer membrane according to  claim 20 , wherein the ionic liquid comprises at least one cation which is selected from the group consisting of NH 4   + , NH 3 R + , NH 2 R 3   + , NHR 3   + , NR 4   + , 1-ethyl-2.3-dimethylimidazolium, P(OH) 4   + , P(OR) 4   + , and PR 4   +  wherein R means methyl, ethyl, propyl or butyl. 
     
     
         26 . The proton-conducting polymer membrane according to  claim 20 , wherein the ionic liquid comprises at least one anion which is selected from the group consisting of F − , BF 4   − , PF 6   − , CF 3 SO 3   − , (CF 3 SO 3 ) 2 N − , CF 3 CO 2   − , the group of sulfates, sulfites and sulfonates of the formula SO 4   2− , HSO 4   − , SO 3   2− , HSO 3   − , R a OSO 3   − , R a SO 3   − , from the group of phosphates of the formula PO 4   3− , HPO 4   2− , H 2 PO 4   − , R a PO 4   2− , from the group of borates of the formula BO 3   3− , HBO 3   2− , H 2 BO 3   − , from the group of silicates and silicic acid esters of the formula SiO 4   4− , H 2 SiO 4   2− , H 3 SiO 4   − , of carboximides, bis(sulfonyl)imides, and sulfonylimides, and mixtures thereof. 
     
     
         27 . The proton-conducting polymer membrane according to  claim 20 , wherein the membrane comprises at least one compound of the formula (P2), 
       
         
           
           
               
               
           
         
       
       wherein R II  in each case mutually independently means a group comprising 1-20 carbon atoms or a residue OR V ,
 in which R V  means H, a group comprising 1-20 carbon atoms or a residue of the formula (P3) 
 
       
         
           
           
               
               
           
         
       
       wherein
 R III  in each case mutually independently means a group comprising 1-20 carbon atoms or a residue OR VI , 
 R IV  in each case mutually independently means O or a group comprising 1-20 carbon atoms, 
 R VI  in each case mutually independently means H or a group comprising 1-20 carbon atoms, 
 q means a number greater than or equal 1. 
 
     
     
         28 . The proton-conducting polymer membrane according to  claim 27 , wherein the membrane comprises phosphoric acid, at least one phosphonic acid and/or polyphosphoric acid. 
     
     
         29 . The proton-conducting polymer membrane according  claim 20 , wherein the membrane contains, in each case relative to the total weight thereof,
 0.5 wt. % to 40.0 wt. % polyazole,   1.0 wt. % to 50.0 wt. % ionic liquid and   10.0 wt. % to 98.5 wt. % compound of the formula (P1).   
     
     
         30 . The proton-conducting polymer membrane according to  claim 20 , wherein the polyazole and the ionic liquid are present in a weight ratio in the range from 1:2 to 1:100. 
     
     
         31 . The proton-conducting polymer membrane according to  claim 20 , wherein the weight ratio of ionic liquid to compound of the formula (P1) is in the range from 1:1 to 1:20. 
     
     
         32 . A method for producing the proton-conducting polymer membrane according to  claim 20 , comprising the steps
 A) mixing one or more aromatic tetra-amino compounds with one or more aromatic carboxylic acids or the esters thereof, which contain at least two acid groups per carboxylic acid monomer, or mixing one or more aromatic and/or heteroaromatic diaminocarboxylic acids, in at least one compound of the formula (P1) or at least one compound which, on hydrolysis, yields at least one compound of the formula (P1), to form a solution and/or dispersion,   B) applying a layer using the mixture according to step A) onto a support,   C) heating the planar structure/layer obtainable according to step B) under inert gas to temperatures of up to 350° C. to form the polyazole polymer,   D) treating the membrane formed in step C) until it is self-supporting, wherein the ionic liquid is introduced into the membrane by   (i) already adding the ionic liquid to the solution or dispersion of step A) and carrying out the following steps B), C) and D) in the presence of the ionic liquid or   (ii) subsequently introducing the ionic liquid into the formed membrane.   
     
     
         33 . The method according to  claim 32 , wherein the mixture of step A) is heated to temperatures of up to 350° C. such that it is possible partly or entirely to dispense with the heating in step C). 
     
     
         34 . The method according to  claim 32 , wherein the mixture of step A) is heated to temperatures of up to 280° C., such that it is possible partly or entirely to dispense with the heating in step C). 
     
     
         35 . The method according to  claim 32 , wherein step A) is carried out in polyphosphoric acid. 
     
     
         36 . The method according to  claim 32 , wherein the membrane is firstly produced, then the compound of the formula (P1) is entirely or partially washed out and then the membrane is reimpregnated with a compound of the formula (P1) and the ionic liquid. 
     
     
         37 . The method according to  claim 32 , wherein
 in step A) at least one compound is used which, on hydrolysis, yields at least one compound of the formula (P1),   the membrane formed in step C) is treated in the presence of moisture at temperatures and for a duration which is sufficient for the membrane to be self-supporting, wherein hydrolysis is carried out using a composition which contains the ionic liquid.   
     
     
         38 . An electrode with a proton-conducting polymer coating, comprising at least one polyazole, at least one ionic liquid and at least one compound of the formula (P1)
   R I   4 POH  (P1)
   
       wherein R I , in each case mutually independently, is a residue which comprises C, O and/or H optionally together with further atoms differing therefrom, wherein two residues R I  may optionally be joined to one another. 
     
     
         39 . A membrane-electrode unit containing at least one electrode and at least one polymer membrane according to  claim 20 . 
     
     
         40 . A fuel cell containing at least one membrane-electrode unit according to  claim 39 .